Electrodeposition of antimony



United States liatented June 21, 1955 brad ELECTRODEPOSITION 8FANTEEEGNY Walter P. Karash, Cleveland, Qhio, assignor to The Har shawChemical Company, Cleveland, Ulric, a corporation of Ohio No Drawing.Application May 1, 1952, Serial No. 285,549

13 Claims. (Ci. 29-1%..6)

This invention relates to antimony plating and to electrodepositedcoatings including a layer of antimony.

Many attempts have been made to produce satisfactory coatings ofantimony but they all have left something to be desired. Poor adherencehas perhaps presented the greatest ditliculties and proposed solutionsof that problem have been very unsatisfactory. Antimony seems to beinherently rather brittle but a deposit characterized by good adherenceand fine texture does not scale and can be very useful since it easilybulls to full brightness, by the use of suitable addition agent can beplated bright or semi-bright, resists corrosion and, when coated withbright chromium, is bright and hard enough for most purposes.

The principal object of the present invention is to produce satisfactoryelcctrodeposited coatings including highly adherent antimony of finetexture and solutions and methods for producing such coatings.

Other objects will be obvious from the following description.

It has now been discovered in accordance with the present invention thatin highpl-l, acid, antimony plating fine-grained, readily buffabledeposits which exhibit remarkable adherence to underlyingelectrodeposits of lead,

tin and silver can be produced by electrolyzing betweenan anode and acathode at a pH in the range from 2.5 to 6.0 a solution containing asoluble antimony compound and an addition agent of the class hereinafterdefined. In producing deposits according to the invention on lead, tinand silver, the antimony very quickly, almost instantaneously, coversthe cathode uniformly instead of initially covering only portions andlater filling out bare areas. These deposits also exhibit excellentresistance to corrosion. For example, a laminar coating made up of0.0002 inch of lead and 0.0008 inch of antimony from a solutionaccording to the invention has been produced which exhibited corrosionresistance (salt spray) superior to that of 0.0010 inch of nickel bothin the as produced state and after deformation of a sheet steel stripcarrying the lead-antimony and the nickel coatings by bending on radiiof less than one-eighth of an inch and then straightening out toapproximate flatness again.

. So far as applicant is aware, no antimony plating process or solutionheretofore known will produce deposits in the pH range from 2.5 to 6.0which will adhere strongly to lead, nor, so far as applicant is aware,will any heretofore known antimony plating process or solution producedeposits at a pH below 2.5 which exhibit the same fineness of grain andstill attain the excellent adherence to lead which applicant attains inthe pH range from 2.5 to 6.0. Bloom (U. S. Patent No. 2,389,131)indicates that good adherence to lead can be had below pH 6 if the leadis first roughened by acid etching or sand blasting. This rougheningtechnique does improve adherence, but it has been found that antimonydeposits from Blooms bath on untreated (that is, unroughened) leadelectrodeposits do not adhere strongly whereas from solutions accordingto the present invention, they do adhere very strongly to untreatedelectrodeposits of lead, tin, and silver and sufficiently well for somecommercial purposes on untreated electrodeposits of copper. Adherence ofantimony electrodeposits according to the present invention to leadelectrodeposits which have been buffed to maximum brightness is equal totheir adherence to untreated electrodeposits of lead. Deposits fromBlooms bath on buffed lead exhibit extremely poor adherence. Thesolutions of this invention exhibit an extremely low rate of immersiondeposition on lead. The corrosion rate of lead in Blooms solution ismore than 50 times as fast as in solutions according to the presentinvention.

The invention then consists in the novel electroplating solutionshereinafter described, the processes which co prise electrolyzing suchsolutions and the novel laminar deposits including: antimonyelectrodeposited on lead, tin, or silver in turn electrodeposited onsteel when the antimony deposit is more firmly adherent and of finergrain size due to the use of one of the novel solutions in itsproduction and therefore has occluded therein a trace of the additionagent; and copper or alkaline antimony on zinc base die castingsfollowed by acid antimony where the final coat of antimony contains atrace of the addition agent as a result of being produced in one of thenovel solutions. By alkaline or acid antimony is meant an antimonydeposit produced in an alkaline or acid antimony plating solutionrespectively.

Examples of antimony halide plating solutions in connection with whichthe invention may be realized in the pH range from 2.5 to 6.0 by theaddition thereto of an addition agent or addition agents as hereinindicated, when electrolyzed between an anode and a cathode whichcathode has a surface of lead, tin, silver, or copper, are as follows,batch compositions being indicated in view of the uncertainty whichexists as to the nature of the complexes formed in solution.

Example I SbFs From to 300, suitably 250 g./l. NH4F From 100 to 300,suitably 200 g./l. NHtOH to give pH From 3.5 to 5 .5, suitably 4.5. H20Remainder.

I Example II SbFs From 100 to 300, suitably 200 g./l. (NH4)2SO4 From 100to 200, suitably 148 g./l. NH'iOH to give pH From 3.5 to 5.5, suitably4.0. H20 Remainder.

Example I]! SbzOs From 100 to 200, suitably 113 g./l. NaFHF From 125 to250, suitably 142 g./l. NH4OH to give pI-I From 3.0 to 5.5, suitably4.5. H20 Remainder.

Example IV SbzOx From 100 to 200, suitably 163 g./l. KRZHF From to 250,suitably 164 g./l. (NI-192804 From 0 to 200, suitably 100 g./l. KOH orNHtOI-l to give pH From 3.0 to 5.5, suitably 3.5. H20 Remainder.

Example V Sb- O From 100 to 250, suitably 163 g./l. NH FHF From 100 to220, suitably 191 g./l. H2804 From 63 to 200, suitably 110 g./l NI-LtOHto give pH From 3.5 to 5.5, suitably 5.0. H20 Remainder.

3 Example VI SbFa From 100 to 300, suitably 200 g./l. HF From to 125,suitably 81 g./l. M onoethanolamine to give pH From 3.0 to 5.5(ordinarily from 100 to 337 g./l.). H2O Remainder.

Example VII SbCla From 100 to 300, suitably 200 g./l. NHeFHF From 100 to200, suitably 145 g./l. NHiOH to give pH From 3.5 to 5.5, suitably 5.0.H20 Remainder.

Example VIII SbCls From 100 to 350, suitably 285 g./l. NH4F From 100 to200, suitably 136 g./l. Rochelle Salts From to 150, suitably g./l. pHFrom 2.5 to 4.5, suitably 4.0.

Example IX SbsOs From 80 to 250, suitably 180 g./l. NH4F.I-IF rom 70 to220, suitably g./l. Glycolic acid From 25 to 100, suitably 52 g./l.NH-IOH to pH From 2.5 to 4.0, suitably 3.0

Example X SbFz From 150 to 250, suitably 179 g./l. (NHUzSO From 100 to200, suitably 132 g./l. Glycolic acid From 25 to 100, suitably 57 g./l.

Examples III, IV, V, and IX should be regarded as basically antimonyfluoride solutions since the SbzOs will react with fluoride to formSbFs. Preferably the antimony halide solutions will contain a fluoridesuch as ammonium fluoride, ammonium bifluoride, hydrogen fluoride,sodium fluoride or potassium fluoride. The solution may also contain anagent such as the Rochelle salt or the glycolic acid for assisting inholding the antimony in solution. The antimony halide should be presentin concentration molecularly equivalent to from 100 to 300 grams perliter of SbF3 and a fluoride should be present in concentrationmolecularly equivalent to from 40 to grams per liter of HP.

The addition agents of the present invention are aromatic sulfonamideswhich term includes substituted sulfonamides, sulfonimides, etc. freefrom double ring groups such as exist in e. g. naphthalene orsaccharine, falling into two structurally similar groups having similaralthough somewhat different effects. These sulfonamides contain anitrogen atom carrying from 1 to 2 aromatic radicals of the structuralform RSO2, where R is a single ring aromatic radical containing sixcarbon atoms.

Group I compounds are of the structural form:

IN: t

where n is an integer from 1 to 2, the aromatic nucleus has six carbons,the free valences of the aromatic nucleus are satisfied by hydrogen andfrom 0 to 3 radicals of the class consisting of Cl, Br, F, OH, OCHs CH3,C2Hs, CO:H, and Nl-Iz and the free valences of the nitrogen atom aresatisfied by from 0 to 2 atoms of hydrogen and from 0 to 2 aliphaticradicals of the class consisting of CI-lzCOOI-I and C2H2OH, the numberof hydrogen atoms being equal to 2 minus the number of said aliphaticradicals.

Group II compounds are of the structural form:

where R is a radical of the class consisting of aromatic radicals of sixcarbon atoms, benzyl and aliphatic radicals having from 2 to 4 carbonatoms, such aliphatic radicals eing made up of carbon and atoms of theclass consisting of hydrogen, oxygen, Cl, Br, and F, the free valencesof each aromatic nucleus being satisfied by hydrogen and from O to 3radicals of the class consisting of Cl, Br, F, CH3, C2H5, CO2H, OH, OCHsand NH: and the free valences of the nitrogen atom being satisfied by aradical of the class consisting of hydrogen and aliphatic radicalshaving from 1 to 4 carbon atoms, preferably alkyl radicals or alkylradicals substituted by Cl, Br, F, COzH or NH2.

When in the above identified addition agents the hen- Zene nucleus isreplaced by the naphthalene nucleus, the benefits of the invention arenot obtained. Expanding group II formula to BzSOzNHSOzBZSOzNHSOzBZ (B2indicating the benzene nucleus) or to destroys the improved effect.Substituting the thiophene or pyridine nucleus for the benzene nucleusrenders the addition agent ineffective. Saccharine (o-benzoyl sulfimide)has practically no effect. Replacing a benzene nucleus by urea destroysthe effect. Cresol, resorcinol, coumarin, naphthalene sulfonic acids,formaldehyde, sulfobenzaldehyde, hypo, clove oil, aloin, chloral,furfural, pyridine, thiourea, salicyclic acid, phenol, glue and manyother common electroplating addition agents were found to beunsatisfactory.

The addition agents should be used in concentration from .2 to 5 gramsper liter. Usually from 2 to 3 grams per liter is satisfactory.

Some specific examples of the compounds of group I are as follows:

Specifiic examples of the compounds of Group II are as follows:

The addition agents of the above indicated classes are effective,without any auxiliary addition agent, to produce grain refinement andmore adherent deposits on the indicated metals and somewhat on roughenedsteel. Compounds of group I tend to give more lustrous and somewhat morebrittle deposits, while those of group II give superior ductility butless lustre although producing fine grained, very white deposits withoutauxiliary addition agents.

The novel class of compounds can be effectively used in combination withother addition agents with the result that there is produced bright ornearly bright deposits having good adherence to lead, copper, etc., andsolutions containing such cooperating addition agents are capable ofbeing operated trouble-free for long periods of time. Examples of suchcooperating addition agents are as follows:

Preferred Preferred range Concentraconcentr ation tion, g./l.

Copper salts, e. g. copper fluoride (CllFz) .l 05-. 2 .1 Polymerizedtetraethylene pentamine 02-. 2 .07

Tartaric emetic; g./l. 150 Rochelle salts g./l. 128 NaOH to "pi-L- 8-43Having thus described the invention, what is claimed is:

1. A process for production of strongly adherent deposits of antimony onmetallic surfaces of the class consisting of lead, tin, copper andsilver comprising electrolyzing between an anode and a cathode having asurface of a metal of the class consisting of lead, tin, copper andsilver, a solution containing a soluble antimony halide and an aromaticsulfonarnide containing a nitrogen atom carrying from 1 to 2 aromaticgroups of the structural form RSO2, where R represents an aromaticradical containing six carbon atoms, said solution being maintained inthe pH range from 2.5 to 6.0 and said aromatic sulfonamide being presentin concentration from 0.2 to 5 grams per liter.

2. A process for production of strongly adherent deposits of antimony onmetallic surfaces of the class consisting of lead, tin, copper, andsilver comprising electrolyzing between an anode and a cathode having asurface of a metal of said class a solution containing a solubleantimony halide and an aromatic sulfonamide having the structural form:

where n is an integer from 1 to 2, the free valences of the aromaticnucleus are satisfied by hydrogen and from 0 to 3 radicals of the classconsisting of Cl, Br, F, OH, OCHs, CH3, C2H5, CO2H, NHz, and the freevalences of the nitrogen atom are satisfied by from 0 to 2 atoms ofhydrogen and from 0 to 2 aliphatic radicals of the class consisting ofCHzCOOI-I and C2H4OH, the number of hydrogen atoms being equal to 2minus the number of said aliphatic radicals, said solution beingmaintained in the pH range from 2.5 to 6.0 and said aromatic sulfonamidebeing present in concentration from 0.2 to 5 grams per liter.

3. A process for production of strongly adherent deposits of antimony onmetallic surfaces of the class consisting of lead, tin, copper, andsilver, comprising electrolyzing between an anode and a cathode having asurface of a metal of said class, said solution containing a solubleantimony halide and an aromatic sulfonamide having the structural form:

radicals having from 2 to 4 carbon atoms, such aliphatic radicals beingmade up of carbon and atoms of the class consisting of hydrogen, oxygen,Cl, Br and F, the free valences of each aromatic nucleus being satisfiedby hydrogen and from O to 3 radicals of the class consisting of Cl, Br,F, CH3, CzHs, COzH, OH, OCH and NH2 and the free valence of the nitrogenatom being satisfied by a radical of the class consisting of hydrogenand aliphatic radicals having from 1 to 4 atoms, said solution beingmaintained in the pH range from 2.5 to 6.0 and said aromatic sulfonamidebeing present in concentration from 0.2 to 5 grams per liter.

4. An antimony plating solution comprising a soluble antimony halide,and an addition agent, the pH of said solution being from 2.5 to 6.0 andsaid addition agent being an aromatic s'ulfonamide containing a nitrogenatom carrying from 1 to 2 aromatic groups of the structural form RSO2-,Where R represents a single .ring aromatic radical containing six carbonatoms, said antimony halide being antimony trifiuoride, being present inconcentration from 100 to 300 grams per liter, said solution alsocontaining an ammonium salt in concentration molecularly equivalent tofrom 100 to 300 grams per liter of NH4F and said addition agent beingpresent in concentration from 0.2 to 5.0 grams per liter.

5. An antimony plating solution as defined in claim 4 furthercharacterized in that said antimony halide is from 109 to 390 grams perliter of SblFa, said solution contain ing an ammonium fluoride inconcentration molecularly equivalent to 100 to 300 grams per liter ofNHF and glycolic acid in concentration from 25 to 100 grams per liter,and said addition agent being present in concentration from 0.2 to 5.0grams per liter.

6. An antimony plating solution comprising antimony trifluoride inconcentration from 100 to 300 grams per liter, dibenzene sulfonamide inconcentration from 0.2 to 5 grams per liter, an acidic material of theclass consisting of alkali metal and ammonium fluorides and sulfates,and an organic compound of the class consisting of glycolic acid andRochelle salts, the pH of the solution being Within the range from 2.5to 6.0.

7. An antimony plating solution comprising antimony trifiuoride in,concentration from 100 to 300 grams per liter, toluene sulfonamide inconcentration from 0.2 to 5 grams per liter, an acidic material of theclass consisting of alkali metal and ammonium fluorides and sulfates,and an organic compound of the class consisting of glycolic acid andRochelle salts, the pH of the solution being Within the range from 2.5to 6.0.

8. An antimony plating solution comprising antimony trifiuoride inconcentration from 100 to 300 grams per liter, chlorodibenzenesulfonamide in concentration from 0.2 to 5 grams per liter, an acidicmaterial of the class consisting of alkali metal and ammonium fluoridesand sulfates, and an organic compound of the class consisting ofglycolic acid and Rochelle salts, the pH of the solution being withinthe range from 2.5 to 6.0.

9. An antimony plating solution comprising antimony trifiuoride inconcentration from 100 to 300 grams per liter, benzene sulfonamide inconcentration from 0.2 to 5 grams per liter, an acidic material of theclass consisting of alkali metal and ammonium fluorides and sulfates,and an organic compound of the class consisting of glycolic acid andRochelle salts, the pH of the solution being Within the range from 2.5to 6.0.

10. An electroplating solution containing a soluble antimony halide andan aromatic sulfonamide containing a nitrogen atom carrying from 1 to 2aromatic groups of the structural form RSO2., Where R represents anaromatic radical containing sixgcarbon atoms, said solution beingmaintained in the pH range from 2.5 to 6.0 and said aromatic sulfonamidebeing present in concentration from 0.2 to 5 grams per liter.

11. An electroplating solution containing a soluble antimony halide andan aromatic sulfonamide having the structural form:

where n is an integer from 1 to 2, the free valences of the aromaticnucleus are satisfied by hydrogen and from 0 to 3 radicals of the classconsisting of Cl, Br, F, OH, OCH;;, CH3, CzHs, COzH, NHz, and the freevalences of the nitrogen atom are satisfied by from 0 to 2 atoms ofhydrogen and from 0 to 2 aliphatic radicals of the class consisting ofCHzCOOH and C2H4OH, the number of hydrogen atoms being equal to 2 minusthe number of said aliphatic radicals, said solution being maintained inthe pH range from 2.5 to 6.0 and said aromatic sulfonamide being presentin concentration from 0.2 to 5 grams per liter.

12. An electroplating solution containing a soluble antimony halide andan aromatic sulfonamide having the structural form:

ii I? aliphatic radicals being made up of carbon and atoms of the classconsisting of hydrogen, oxygen, Cl, Br and F, the free valences of eacharomatic nucleus being satisfied by hydrogen and from 0 to 3 radicals ofthe class consisting of Cl, Br, F, CH3, C2H5, COzH, OH, OCH: and NH: andthe free valence of the nitrogen atom being satisfied by a radical ofthe class consisting of hydrogen and aliphatic radicals having from 1 to4 atoms, said solution being maintained in the pH range from 2.5 to 6.0and said aromatic sulfonamide being present in concentration from 0.2 to5 grams per liter.

13. An article of manufacture comprising a ferrous metal body, anadherent coating of lead overlying said ferrous metal body and anadherent coating of antimony overlying said coating of lead, saidcoating of antimony having been applied upon an unroughened surface ofsaid lead coating, and said antimony coating being fine grained andadherent and having occluded therein a trace of an aromatic sulfonamidecontaining a nitrogen atom carrying from 1 to 2 aromatic groups of thestructural form RSOz, where R represents an aromatic radical containing6 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS1,780,944 Roscher Nov. 11, 1930 2,191,813 Brown Feb. 27, 1940 2,389,131Bloom Nov. 20, 1945 2,441,810 Glover et a1 May 18, 1948

13. AN ARTICLE OF MANUFACTURE COMPRISING A FERROUS METAL BODY, ANADHERENT COATING OF LEAD OVERLYING SAID FEROUS METAL BODY AND ANADHERENT COATING OF ANTIMONY OVERLYING SAID COATING OF LEAD, SAIDCOATING OF ANTIMONY HAVING BEEN APPLIED UPON AN UNROUGHENED SURFACE OFSAID LEAD COATING, AND SAID ANTIMONY COATING BEING FINE GRAINED ANDADHERENT AND HAVING OCCLUDED THEREIN A TRACE OF AN AROMATIC SULFONAMIDECONTAINING A NITROGEN ATOM CARRYING FROM 1 TO 2 AROMATIC GROUPS OF THESTRUCTURAL FORM RSO2-, WHERE REPRESENTS AN AROMATIC RADICAL CONTAINING 6CARBON ATOMS.